A light emitting push button

Abstract: The present invention relates to a light emitting push button for operating purposes, for instance a number button on a telephone apparatus, wherein the push button includes a body which is double-molded from two different plastic materials, of which one material is light conductive and the other is opaque. A light emitting device, such as a light emitting diode, is arranged to emit light on the underside of the push button so that the light is conducted through the light conductor material and is emitted on the upper side of the button. According to the invention a slot (5) is formed between the light conductive material (3) and the opaque material (2) on the upper side of the button (1), such that light conducted through the light conductive material (3) will be scattered uniformly and therewith visible from all directions.

Description: TECHNICAL FIELD The present invention relates to a light-emitting push button according to the preamble of claim 1, as for example known from US-A-4 924 044. DESCRIPTION OF THE BACKGROUND ART Light-emitting push buttons of the aforedescribed kind are known to the art. Although the majority of existing buttons provided with light conductors light up well, there is often an angle or angles of incidence at which the light almost disappears, depending on the line of sight. The lens requires free surfaces around the lens, in order for the light to be reflected from the sides and so as to obtain the best possible light yield at the top of the button. A light conductor integrated in such a double-molded button, for instance in telephone apparatus, makes it difficult to discern whether the button is lit or not when viewed in a direction towards the button, because the light is not scattered uniformly at the upper surface of the button. This is because the material in the button and the lens is fused or migrated together by heat in the molding process, and the light reflections in this part is "extinguished" or dampened out. A light conductor which is completely molded in would dampen the reflection of light excessively. SUMMARY OF THE INVENTION An object of the present invention is to avoid the drawback of not being able to see the light from all directions, and to provide a press button in which light is scattered uniformly at the top of the button, such that the light yield at the button top will be the best possible for all angles of incidence. This object is achieved by forming an air gap or slot which extends to slightly below the top of the lens, between button and lens, so that light will be reflected against the lens surface thus exposed. An inventive push button affords the advantage that the light yield will be practically uniform in all directions, or in other words there are found no angles of incidence at which the light will disappear irrespective of the line of sight, but that the button will be clearly visible from all directions. The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a perspective view of an inventive light emitting push button; and Figure 2 and Figure 3 are perspective views of alternative embodiments of an inventive light-emitting push button. BEST MODE OF CARRYING OUT THE INVENTION Figure 1 illustrates in perspective a preferred embodiment of a light-emitting push button 1. The push button 1 is ellipsoidal in shape and includes a double-molded body of opaque material 2 and a light conductive material 3 respectively. The light conductive material 3 can be considered to form a lens through which light can be conducted from the underside of the button, for instance from a light emitting diode or like device (not shown), up through the lens and radiate from the upper side 4 of the button. By providing an air slot 5 between the opaque material 2 and the lens 3 down to a distance of about 4 mm from the lens top, light is able to reflect against the thus exposed surface 6 of the lens. The slot 5 located between the aforesaid different materials need only have a width of some tenths of a millimeter in order for the desired reflection to be achieved, although from a tool/technical aspect the slot will have a width of about 0.5 mm in practice. Some of the details concerning the design of the press button with regard to its attachment to the equipment to which it belongs, or other elements that are dependent on the function of the push button have not been shown in the drawing. The design of these details and elements will be obvious to one of normal skill in this art and form no part of the present invention. The push button 1 need not, of course, have the ellipsoidal shape shown in Figure 1. Other designs may incorporate the same technical solution, for instance the round press button shown in Figure 2 and the rectangular press button shown in Figure 3. The same reference numerals have been used in these latter figures as those used in Figure 1. Press buttons of other designs than those shown may also incorporate the inventive solution. It will be understood that the invention is not restricted to the aforedescribed and illustrated embodiment and that modifications can be made within the scope of the following claims.

Claims: A light emitting push button (1) for operating purposes, for instance a number button on a telephone apparatus, wherein the push button (1) includes a body which is double-molded from two different plastic materials (2,3), of which one material (3) is light conductive and the other (2) is opaque, and wherein a light emitting device, such as a light emitting diode, is arranged to emit light on the underside of the push button (1) so that the light is conducted through the light conductor material (3) and is emitted on the upper side (4) of the button (1), characterized by a slot (5) formed between the light conductive material (3) and the opaque material (2) on the upper side of the button (1), such that light conducted through the light conductive material (3) will be scattered uniformly and therewith visible from all directions. A light emitting push button according to claim 1, characterized in that the slot (5) extends to a depth of about 4 mm from the upper side (4) of the button (1). A light emitting push button according to claim 1 or claim 2, characterized in that the slot (5) has a width of 0.5 mm.

Inventors: LARSSON STIG TORBJOERN, LARSSON, STIG TORBJOERN, Larsson, Stig Torbjörn
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON
Application year: 1994
Main classification: H01H9
IPC codes: H01H13, H01H9